American military officials say that the planning figure is 25,000 troops, commanded by a three-star general. They would include trainers as well as thousands of Green Berets and other special operations troops who would work with Afghans on counter-terror missions. NATO would be asked to contribute troops, but it's likely that the U.S. would contribute the bulk of those forces.

The Afghan troops face a number of hurdles before they can assume full responsibility. Illiteracy is one of them. The U.S. is trying to bring soldiers up to first grade level and officers up to third grade level. Only about 20 percent of Afghan forces have the educational abilities needed to go on to more advanced schools, such as for logistics or planning.

One U.S. officer says that not only can many Afghan soldiers not read or write, but many can't even count. The U.S. tries to get around that in some novel ways. In some cases trainers draw a rectangle in the dirt for Afghan commanders who can't tell how many soldiers they should have. The Americans say that if the soldiers standing at attention fill the rectangle, that's a full complement.

The attrition rate for the Afghan forces is nearly double what it should be and the lack of junior leaders is another problem. The Afghans have a deficit of thousands of needed sergeants, considered the backbone of any army.

[NPR Pentagon correspondent Tom Bowman filed for us from Afghanistan, where he's on assignment.]

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